Occulter for searchlights



Jam" 9 1940. Q CLQUSTQN 2,186,063

OCCUL'IER FOR SEARCHLIGHTS Filed June 17, 1937 2 Sheets-Sheet l INVENTOR@MHLES @0116 mm Jan. 1940- c. E. CLOUSTON 2,186,063

OCCULTER FOR SEARCHLIGHTS Filed June 17, 1937 2 Sheets-Sheet 2 PatentedJan. 9,

UNITED STATES PATENT OFFICE (MJCULTER FOR SEARCHLIGHTS Application June17, 1937, Serial No. 148,655 In Great Britain June 29, 1936 9 Claims.

This invention relates to occuiters for searchlights, particularly forthose employing electric arcs.

When a Searchlight is extinguished the carbuns-or the incandescent lampfilaments if used-continue to glow for some little time with the resultthat the Searchlight continues to be visible. This is inconvenient inWar conditions or when. the searchlight is being used for signalling. Toovercome this disadvantage it is already known to provide means so that,when the current is switched off or the are is broken, the residuallight from the still glowing source intercepted. Such means are known asecctdters. it is also known to provide means whereby the occulter'ismoved automatically into the occulting position toe current is cut ofior the are is broken, and is moved automatically into a nonoccultingposition when the supply is switched on or the arc is clruck.

The do of an occulter is a matter of some diiiiculty. it has beenproposed to provide shutters across the front the usual searchlightcasing or drum but either these are large and expensive in constructionand operation, or they are unreliable, or slow in action, or theyobstruct a considerable amount of light in the non==occulting positionand so reduce the beam candle power available. Usually they sufier fromseveral if not all, of these disadvantages. lt'ioreover the search-=light drum has to be specially designed for them, whereas it isdesirable that the lamp and mechanism should be capable of being used ina standard proiector.

It has also been proposed to provide a small occulter for are lampswhich should move up and almost totally enclose the glowing carbons inthe occultirig' position, so as to cut oil" practically all the light.During operation of the light, such occulters were moved into anon-occulting position for which a position in the shadow of the fixedparts of the lamp was selected, so that the occulter should notintercept any more light than was necessarily already obstructed in anycase. These requirements, together with that of avoiding the operatingmechanism, involved the necessity for the occulter to move aconsiderable distance, and this made it slow in operation, or liable todamage. On the other hand, since the occulter had to be small and yet toenclose the glowing carbons closely, it was liable to become burned orto give rise to short circuits or to interfere with rapid are striking.The fact that the heat was totally enclosed naturally increased thedanger of burning.

Searchlights are usually provided with a refiector or mirror for thepurpose of greatly increasing the beam candle power. When the light isextinguished, the mirror greatly increases the beam candle power fromthe residual glow, and it is this that makes the Searchlightstillvisible.

To provide an emcient occulter,itisthereforeonly necessary to interceptlight from the source to the mirror and the interception of the directlight from the source is relatively unimportant. Some of this directlight is intercepted in any case by the fixed parts of the lamp and theamount intercepted may be increased by fixed screens. not moving withthe occulter.

According to the present invention an occulter is provided comprisingone or more screening surfaces so shaped and positioned that in thenon-occulting position they lie substantially parallel to the axis ofthe lamp, and therefore edge on to the light proceeding from thereflector or mirror. According to the invention also, the screeningsurface is movable into an occulting position in which it intercepts thelight proceeding from the carbons to the reflector or mirror. Additionalfixed screens may or-may not be provided to cut off some or all of thedirect light from the carbons.

The invention enables situations to be used for the non-occultingposition of the occulting surfaces that could not be used in the, priorart. Previously, as has been mentioned, situations were sought in theshadow of existing parts: as a result of the present inventionsituations in the lamp casing or drum remote from all operating parts ofthe lamp can now be used as the nonocculting or open position of theocculter'. This simple lamp design, allows larger occulting surfaces tobe used, thus promoting cooling, and also allows a short occultermovementto be employed, 1. e. allows the occulting and non-occultingpositions to be relatively near each other. From this last consequenceit follows that the occulter may be operated quite rapidly.

According to my preferred construction asingle movable occulting memberis employed, pivotable about a horizontal axis so that it moves from anocculting position between the carbons and the reflector or mirror intoa non-occulting position above the positive carbon and clear of the tailflame. In this construction the movable occulting member is preferablyof the form of a plate with two side walls or else in the form of a partof a cylinder. In the occulting position gaging flanges may m providedon the fixed and moving members so as to maize the hon light tight. Afurther feature of this construction is that the fixed screen may beconstructed as an open box casting solidly connected to both thepositive and negative heads oi the the positive and negative carbonsboth passing through the sides of this box. This construction allows aperfect light seal to be obtained.

The invention will now be described more fully with reference to theaccompanying drawings in which Fig. 1 is a side elevation of a form ofthe occulter comprising a single movable member swingable about ahorizontal ans. The occulter is shown both in the open and clmedpositions relative to the parts oi the lamp with which it co-operates.

Fig. 2 is a perspective view of the movable occulting member of theocculter shown in Fig. 1.

Fig. 3 is a perspective view of the fixed member with which the movableocculting member or Fig. 2 co-operates to form a light-tight box whenthe movable member is in the closed position.

Referring to the construction of occulter shown in Figures 1, 2 and 3,the single movable occul t ing member employed is in the form of a plate23 with side walls 24 and 25: the plate 231s shown as a flat plate, butcould equally well be in the form of a half cylinder. The edges 25 ofthe side walls 26 and 25 and plate 23 are bent over so as to form acontinuous groove 26 around three edges of the occulting member, Fig. 2.

In the occultimg position (shown in full lines in Figure l) theocculting member fits (like a hood) over a fixed V-shaped member Zl inthe manner shown in Fig. 1 whereupon a projecting edge portion 28 formedon the vertical limb of the fixed member engages in the groove 28 or themovable member. A groove 2% is formed around the edge of the inclinedlimb of the fixed member 21 and in the occulting position of the movablemember the edge 36 thereof engages in this groove. The grooves 26 and 29in the movable and fixed members respectively may be lined with softmaterial, e. g. asbestos packing to form a bedding in which the edges 28and 38 may rest, thus promoting light-tightness.

In Fig. 1 the movable member of the occulter is shown in the occultingposition in full lines and in the open or non-occulting position inbroken lines, both in relation to an arc lamp. In this figure thereference numeral 35 indicates the positive carbon, 2 is the negativecarbon, 35 is the positive nose cap and its is the negative nose cap.Both nose caps are shown as being of fabricated construction but couldequally well be castings- Ihey ares'upported by, but insulated from, thefixedme'mber 2i of the occulter. In this form of lamp, both nose capsbecome red hot in use and it i's necessary to screen them. We thereforeenclose them by annular projections 35 and fiforming parts of the fixedmember 21'. As a fur her precaution an annular recess 3! is formed inthe negative carbon jaws to and 39 and encloses the lower end of thenose cap 3t and of the annulus 36. A similar recess could equally wellbe made in the positive carbon jaws.

The movable occulting member is carried by arms which are attached to a.shaft M by means of the flanged bosses 32. A lever is also attached tothe shaft ll for the purpose of rockjournalled in a bearing or bearingsIorming of the bracket 45.

The occulter may also be linked with an arcstriking electrode 46 whichmay be carried inside the fixed member 211 or the occulter or ln'arecess formed in part of the positive head. This are striker, which iselectrically connected to the positive carbon, is shown as bemg carriedon the shaft Al .irnalled in bearings 5| (Fig. 3) formed in the .xedmember 2'! of the occulter. To the shaft 4'! is secured a lever 48 whichis coupled by the link 49 to a similar lever 50 fastened to the shaft4!. The arrangement of these levers and links is such that when theshaft 4| is turned by the turning means provided in the base, it causesthe occulter to move from the closed position as shown in full lines tothe open position as shown in broken lines and at the same time causesthe arc-striking electrode 4' to move from a position in contact withthe negative carbon 32 to a position under the positive carbon 3i thuscausing in well-known manner an arc to be struck between the negativeand positive carbons 32 and 3|.

This construction solves the problem of combining arc-striking andocculting without allowing light leakage by a novel principle which isto put the movable arc-striking electrode permanently inside the limitsof the enclosed box formed by the occulter in its closed position.

It will be noticed also that the conception of this occulter isradically different from that of the prior art. Whereas in earlierconstructions the occulter comprised one or more movable parts whichwere additional to the main structure of the lamp and had to close overthe carbons and adjacent parts to cut off light as best they could, thepresent structure comprises a more or less closed -\I-shaped box havinga movable lid, (to which are attached the sides of the box in the formshown).

The fixed box is incorporated as part of the lamp structure and is givenas complicated form. as may be necessary to enclose the carbons, nose-,caps, and any other parts from which light may issue. It is clear fromFig. 1 that light-tightness, against light coming from the glowingcarbons and nose-caps, not only indirectly but also by re-= flectionfrom the parts of the lamp, may be obtained by this type of constructionof a totally clifierent order from anything possible with two or moremoving occulting members that have to avoid existing parts of the lampin their movements. Q

What I claim is:

1. A searchlight occulting device comprising the combination with ahousing enclosing the electrode tips on at least two sides, a movablescreening member swingable vertically about a. horizontal axis from theocculting to the nonocculting position and so shaped that in itsocculting position it encloses said tips on all other sides and in itsnon-ocoulting position its screening surface lies substantially edge-onto the beam reflected by the Searchlight.

2. A searchlight occulting device comprising a. movable screeningmember, swingable vertically about a horizontal axis from the occultingto the non-occulting position and so shaped that in its non-occultingposition its screeningsurface lies substantially edge-on to the beamreflected by the Searchlight, and a. fixed occulting member cooperatingwith the movable member.

3. The combination with a searchlight comprising a substantiallyhorizontal positive carbon and an inclined carbon, operating mechanismthere? for, reflecting means and a lamp casing, of an occultingmechanism comprising a fixed member andi a movable member, the fixedmember being in the form of a V-shaped plate having one limb located asa vertical screen through which the positive carbon projects and theother limb located as an inclined screen through which the negativecarbon projects, and the movable member being a hood shaped plate whichin the nonocculting position lies with its screening surfacesubstantially edge-on to the reflected beam and in its occultingposition fits hood-like over the fixed member to constitute asubstantially closed box around the ends of the carbons.

4. The combination of a searchlight and occulting mechanism according toclaim 5, the co-op crating edges of the fixed occulting member and themovable occulting member being inter-fitting in relation to one anotherto ensure lightformed as annular projections circumferentiallysurounding said carbons.

6. A searchlight occulting device comprising movable occulting means ofsheet form which in the non-occulting position lie with the screeningsurface substantially edge-on to the searchlight beam, and anarc-striking electrode located inside the limits of the occulting devicewhen in the occulting condition.

'7. A searchlight occulting device according to claim 6, including asingle means for actuating the occulter and for actuating thearc-striking electrode. r

8. A searchlight occulting device comprising the combination with ahousing enclosing the electrode tips on at least two sides, a singlemovable screening member swingable about an axis located to one side ofsaid tips from the occulting to the non-occulting position and so shapedthat in its occulting position it encloses said tips on all other sidesand in its non-occulting position its screening surface liessubstantially edge-on to the beam reflected by the searchlight.

9. In a combined occulting and are striking device for searchlights, thecombination with electrode holders enclosing the arcing tips on at leasttwo; sides, an occulting means of sheet form which in the occultingposition encloses the said tips on their other sides, a movable arestriking electrode within the enclosure formed by said occulting meansand movable from one electrode to the other. said are striking electrodebeing at all times located within the overall dimensions of saidenclosure.

CHARLES EDWARD CLOUBTON.

